Typically, the human stomach secretes approximately 2 liters of hydrochloric acid daily which is a strong acid secreted by the gastric parietal cells. Hydrochloric acid plays an important role in digestion, both directly (i.e., by reducing large food particles in size) and indirectly (i.e., by activating some of the gastric enzymes, such as pepsin).
Normally, the walls of the stomach and small intestine are protected from the potentially damaging effects of this strong acid. For example, the mucosal surface of the stomach is lined with cells which secrete a slightly alkaline mucus, which covers the stomach surface and serves to neutralize hydrogen ions, thus serving as a chemical barrier between the acid and the cells. Further, the cell membranes which line the stomach have limited permeability to hydrogen ions, which are prevented from entering into the underlying mucosa. Constant replacement of the mucus cells which line the stomach walls also helps protect the mucosa.
Despite these protective mechanisms, in many people, the gastric and duodenal mucosa becomes eroded or ulcerated and the damage may be very severe. The causes of such gastric or duodenal erosions or ulcers are unknown, but are regarded as a combination of an imbalance between progressive and protective factors. Many methods of treating ulcers and the accompanying pain, including administration of a variety of drugs to prevent or reduce acid secretion, to buffer the effects of secreted acid, and to coat the gastric mucosa with a protective film, have been tried. Although there are presently numerous drugs of value in such treatment, each has limitations. Particularly useful would be an agent or drug effective in reducing or preventing acid secretion by parietal cells because such an agent or drug would make it possible to minimize the quantity of acid present in the stomach and duodenum and, thus, avoid further irritation of or damage to either organ.